Method and apparatus for electromagnetic shaping of metallic bodies



Oct. 19, 1965 KIYOSHI INOUE 3,212,311

METHOD AND APPARATUS FOR ELECTRO-MAGNETIC SHAPING OF METALLIC BODIES Filed April 16, 1963 5 Sheets-Sheet 1 21b KIYOSHI INOUE INVENTOR. 8 x -I 3 FIGZ BY a AGENT Oct. 19, 1965 KIYOSHI INOUE METHOD AND APPARATUS FOR ELECTRO-MAGNETIC SHAPING OF METALLIC BODIES 5 Sheets-Sheet 2 Filed April 16, 1963 FIG.4

33 31a 32b 32c a KIYOSHI INOUE INVENTOR.

FIGS) Oct. 19, 1965 wosl-n INOUE 3,212,311

METHOD AND APPARATUS FOR ELECTED-MAGNETIC SHAPING OF METALLIC BODIES Filed April 16, 1963 3 Sheets-Sheet 3 REvEFzswaLE VAEAEEE FEEQUENCY 75b A-C SOURCE REVERSIBLE VARIAIBLELSPFLED' OTOR KIYOSHI INOUE INVENTOR.

United States Patent 3,212 311 METHOD AND APPAR ATUS FOR ELECTRO- MAGNETIC SHAPING 0F METALLIC BGDIES Kiyoshi inane, 182 S-chome, Tamagawayoga-machi, Setagaya-ku, Tokyo-to, Japan Filed Apr. 16, 1963, Ser. No. 273,480 Claims priority, appiication Japan, Apr. 17, 1962, 37 15,7 61 12 Claims. (Cl. 72-16) My present invention relates to methods of and an apparatus for shaping bodies and, more particularly, to the forming and shaping of metallic bodies without physical contact with the workpiece.

Heretofore it has been the practice to shape metallic bodies in a plastic state with the aid of mechanically applied pressure of a continuous or discontinuous nature. Among the continuously applied forces serving to form a metallic body, one may note the drawing of wire or other elongated members through a drawing die, the extrusion of elongated elements through dies and methods of hot and cold pressing. Intermittently applied forces are used in the repeated rolling of metal ingots and billets, the forging of metal objects and stamping techniques. All of these prior-art methods are characterized by direct physical contact between the body to be shaped and a tool by means of which the high pressure is applied. Since the wear of such tools is a prime consideration in the economy of a forming process, considerable elfort has been made to develop high-strength alloys with a commensurate increase in the costs of the apparatus. Moreover, contamination of the workpiece by the tool and adhesion of the workpiece to the tool is frequently significant. The drawbacks of these earlier methods have restricted the field of application of these techniques to a few exceptionally suitable metals and alloys and require special procedures when other materials are to be used.

It is an object of the present invention, therefore, to provide a method of and an apparatus for the noncontact shaping of metallic bodies.

A more specific object of the present invention is to provide the method of drawing elongated metal members without the use of the expensive dies previously required.

Still another object of my invention is to provide a method of bonding an outer metallic sheath to an inner metallic core without the aid of high static pressures and ambient temperatures.

Yet another object of the invention is to provide an apparatus capable of magnetically shaping metal bodies continuously.

In accordance with the present invention, these objects are attained by applying to a metallic body a compressive electromagnetic force adapted to reduce the cross-section of a body, which is in a plastic state during the application of this impulsive electromagnetic force. I have discovered that it is possible to magnetically shape a metallic body by surrounding it with one or more coils through which an impulsive electric current is passed for exerting upon the body an inward force. The principle of the present invention derives from the fact that, when a strong magnetic flux is developed by the passage of an electric current through the coil, a magnetic inductive force is developed which applies mechanically effective compression to the body surrounded by the coil. While most persons familiar with the principles of electromagnetic fields are aware that a magnetic inductive force results in an axial pressure upon the body (e.g. in the manner of a solenoid coil), it must be understood that this axially directed force is but one of the components of the inductive force field 3,212,311- Patented Oct. 19, 1965 surrounding each turn of the coil. The other component can be considered an inwardly directed or radial force which can, according to the present invention, be employed to shape solid bodies. While the inwardly effective radial force of a magnetic coil has been employed hitherto as a magnetic bottle to confine a conductive gaseous plasma, to my knowledge there has been no suggestion to the effect that the impulsive radial force of a coil can serve to reduce permanently the cross-section of a solid and a not necessarily inherently charged body by bringing it to a plastically deformable state and then applying inwardly effective magnetic force thereto. While best re sults are obtained with materials having a high magnetic permeability, it has been found, surprisingly, that substantially all conductive bodies in which an electric current can be magnetically induced, can be employed within the principles of the present invention.

According to a more specific feature of this invention, the body is surrounded by a plurality of axially spaced coils which can be energized successively for applying an axially shifting radial force to the body, thereby tending to draw it axially in addition to radially compressing it. This technique is particularly suitable for the drawing of tubes, bars, wire and the like. The axially offset coils may be connected in series or in parallel in a common circuit and are advantageously provided with respective capacitive means bridged thereacross or connected in series therewith. It is possible, for example, to employ the electromagnetic coils as the inductances of a delay line and thus to establish, in effect, a traveling wave in the form of a radial force pulse which sweeps the body along the area of coils. Similarly, the capacitive means can form resonant networks with the coils which simultaneously or successively discharge to provide the force pulses. It should be noted that sheets and other nonround bodies can be shaped by the present method with appropriately configured electromagnetic coils.

The apparatus employed in the present invention can also make use of servo techniques to control the parameters of the electromagnetic force field in response to the dimensions of the output workpiece in order to yield bodies of uniform cross section.

It is also contemplated, in accordance with the present invention, to provide a metallic body with a sheath of a dilferent material and to bond this material to the core. The sheath may be deposited in any fashion (e.g. by electrodeposition, dipping or spray coating) and is firmly welded to the core under the inductive heat developed as the body passes through the coil. The squeeze or pinch effect of the electromagnetic field serves to provide the pressure necessary for firm bonding. According to yet another aspect of this invention, the core and sheath are relatively oscillated at sonic or supersonic frequencies to generate sufficient heat at their interface to cause the interdilfusion of the two metals and produce a metal-clad body whose surface layer is permanently aflixed to a core. It is desinable, in this technique, to establish a traveling sonic wave in one or the other of the materials, thereby causing the frictional effect to progressively sweep the entire length of the interface.

The above and other objects, features and advantages of the present invention will become more readily apparent fro-m the following description, reference being made to the examples demonstrating the principles of the present invention and the accompanying drawing in which:

FIG. 1 is an axial cross-sectional view of a basic apparatus for drawing elongated metallic bodies according to the invention;

FIG. 2 is a view similar to FIG. 1 illustrating the production of metal-clad bodies in accordance with the present method as well as a modified circuit constituting part of the apparatus for carrying out the method;

FIG. 3 is another axial cross-sectional view to illustrate how the present technique can be applied to sheet materials;

FIG. 4 shows a circuit diagram of an apparatus Wherein the electromagnetic coils form respective parallelresonant networks;

FIG. 5 shows an apparatus wherein the parallel-resonant networks are connected in series;

FIG. 6 is an idealized diagram of a coil showing the principles of the present invention;

FIG. 7 is a diagrammatic view illustrating another apparatus for carrying out the invention;

FIG. 8 is a similar view of a modified apparatus;

FIGS. 9 and 10 illustrate further modifications of a magnetic forming system; and

FIG. 11 illustrates an apparatus for producing metalclad bodies by isolation.

In FIG. 1 I show an arrangement wherein a metallic wire 10 is reduced in cross-section and magnetically drawn by passing it through a plurality of axially spaced coils 11,: 12, 13 and 14. A takeup reel or drum 15 is rotated by a motor not shown and draws the wire through the coils at a constant rate. The coils are connected in series and are bridged by a capacitor 16 which can be charged through a resistor 17 by a battery 18. The ca pacitor 16 can form, with the total inductance of coils 11-14, a resonant network which periodically applies electric pulses to the coils and simultaneously induces in the continuously moving wire 10 an clectromotive force. The inductive etfect of the coils 11 is to accelerate the wire 10 in the direction of its displacement (arrow 19) and simultaneously to apply thereto a compressive force. The wire 10 can be heated prior to passage through the coils but is, in this case, heated inductively by virtue of the fact that the high-frequency-pulsed current seen by the coils 11-14 is sufiicient to raise the wire to a temperature in which it is plastically deformable. From FIG. 6 it can be noted that the magnetic field surrounding the wires of the coil 60 has concentric field lines 61 which can be resolved into a net axial force represented by vector 62 and balances inward forces represented by vectors 63. The latter forces are the ones exploited to shape the metal bodies.

Example I A piano wire of high-carbon steel is drawn and tempered in an apparatus of the general type shown in FIG. 1 from a diameter of 5 mm. to a diameter of about 4 mm. The wires are passed through five coils similar to coils 11-14 or through one of these coils five times at a rate of 4 m./sec., the coils having about 500 turns. The discharge of capacitor 16 and, therefore, the magnitude of the electrical pulse passed through the coils is approximately 5000 joules/see, the pulse duration being approximately 30 microseconds and the magnetic flux it dt applied during each pulse equal to approximately 7.5 X10 gauss/sec. Approximately 50 kw. of power is used to produce about 5 kg. of wire and the DC voltage (e.g. of battery 18) is approximately 20 volts. A wire temperature of approximately 900 C. is developed in the region of the coils which have an axial length of 10 cm. and an inner diameter of about 10 mm. The period between pulses can be 3040 microseconds. The resulting wire is found to be tempered to the austenitic level and to have a hardness of 780 Hv as measured by Vickers hardnesstesting machines, and a tensile strength in excess of 20 '2.- tons/cm. an increase of 10-15% over the tensile strength of piano wire tempered in a conventional furnace and drawn by the usual dies.

FIG. 2 shows an arrangement whereby metal-clad wires having important industrial application can be made with ease by the present method. It has long been desired to be able to produce, for electrical transmission purposes, wires having a core of a metal with a high tensile strength and a sheath of a highly conductive metal whose inherent tensile strength is less than that necessary for transmission lines spanning large areas. Various efforts have been made to provide steel wires with copper or aluminum sheaths to solve this problem. Basically, these earlier methods involved the coating of the steel wire with aluminum or copper and its subsequent heat treatment in annealing furnaces to cause fusion at the interface of the two materials. None of these efforts were, however, successful since no firm bond could economically be established between the core and the sheath without adversely affecting the tensile strength of the inner steel member. With the aid of an apparatus such as that shown in FIG. 2 it is possible to ensure a more successful bonding of the two materials together. A wire 20 consisting of a core 20a having a relatively low conductivity but a high tensile strength is surrounded by a sheath 20b of highly conductive material. The two portions of the wire need not be in intimate contact and may even have a gap of from 5 to 10 microns between them prior to the forming operation. As indicated in FIG. 2, the wire passes initially through a coil 21 whose high-frequency alternating-current source 21a is of relatively low power but is capable of efiecting a preliminary inductive heating of the core 20a and, possibly, the sheath 20b. The wire is continuously displaced in the direction of arrow 28 by a takeup reel, not shown, and then passes through coils 22 and 23 which carry out the magnetic forming. A capacitor 26 is connected across these two coils 22 and 23 which are coupled in parallel for simultaneous energization. Capacitor 26 is charged via a resistor 27 from a rectilfier bridge 28 supplied by the secondary winding 28a of a saturable transformer 28' whose primary winding 28b is energized by an alternating-current source 28c. The biasing winding 28d of this transformer is connected in series with an adjustable resistor 286 for setting the D.-C. bias level of the transformer and a battery 28 A pair of sensing rollers 28g engage the output end of the wire 20 and are responsive to its diameter. When the resistance across the wire falls as a consequence of an overreduction in its cross-section by the magnetic coils 22, 23, a larger current flows in the biasing winding 28d to increase the degree of saturation of transformer 28 and lower the intensity of the pulse current applied to these coils. An increase in the diameter of the wire will, cor respondingly, produce an increase in the pulse current and, thereby, increase the compressive force applied to the body. This feedback arrangement constitutes servo control of one parameter of the electric current applied to the coils, namely the amplitude.

The high-frequency alternating-current generator 21a can be a variable-frequency oscillator whose control element (e.g. a variable capacitor or inductor) is driven by a conventional servomotor 2112 from a servoamplifier 210 in accordance with the potential drop along the wire 20. This servo arrangement is such that a decrease in the resistance or voltage drop between the rollers 28g and a roller 21g will cause an increase in the output frequency of source 210 to raise the heating effect of coil 21, thereby rendering the wire 20 more plastic along its forming portion in the region of coils 22 and 23. Each force pulse of the latter coils will, consequently, have greater effectiveness in reducing the cross-section of the wire.

Example 11 A steel core 20a is provided with a copper sheath 20b by dipping or electrodeposition, although mere insertion of the core within the sheath is also possible. I have found that excellent results are obtained in this manner even when there is between 5 and microns of play between sheath and core. The wire is passed through an apparatus of the type shown in FIG. 2 at a rate of about 2 m./sec. while a pulse energy of 2000 joules/sec. is applied by the capacitor 26 to the coils 22, 23. The pulse spacing and duration is approximately 100 microseconds. The coils each have approximately 500 turns as previously noted. The core has an initial diameter of about 5 mm. While the copper sheath has a radial thickness of 0.1 mm., the wire being reduced by the magnetic field to a total diameter of 4.5 mm. Examination of the wire crosssection indicates that the sheath is intimately bonded to the core and repeated bending tests show that there is little tendency for the outer conductive layer to flake otf from the core. No reduction of the tensile strength of the steel wire is found; the final product is suitable for use in electric transmission lines and has the tensile strength to be expected of a steel wire having a diameter of 4.5 mm. and an electrical conductivity greater than that to be supplied by the copper sheath alone.

FIG. 3 shows another apparatus for the magnetic draw forming of metal bodies. A steel sheet 30, emerging from a heating furnace 31, passes through forming coils 32a-32c and 33a, 33!) which have an oval configuration to permit the sheath to pass therethrough. It may be seen that the individual coils 32a and 32b effect the preliminary shaping of the sheath and are closely juxtaposed to have the effectiveness or flux intensity (e.g. as measured in ampere turns) of twice the flux intensity of an individual coil such :as that shown in 320 longitudinally spaced from coil 32a, 32b. Similarly, coil 33a has twice the number of turns of coil 32b and, therefore, is able to supply twice the magnetic flux for shaping purposes although it is composed of a single coil. Intermediate coils 32c and 33a there is provided a further heating device 31a for again raising the temperature of the sheath 30 to bring it to a plastic state. In this case, electrically resistive heating is used. The device comprises transformer 31]; whose output is bridged across a pair of rollers 31c conductively engaging the sheath 30 at spaced locations. A high-frequency alternating-current source 31d supplies the transformer.

As will be readily apparent from FIG. 3, the coils 32a-32c and 33a, 33b are each associated with a respective capacitor 36a-36e and are incorporated in a delayline network across which a direct-current source 300 is connected via an amplitude-control resistor 37 which, in part, determines the time constant of the delay line. A mercury-vapor tube or a thyratron 38a is bridged across the delay line and is provided With a triggering circuit 38b of conventional type for intermittently discharging the delay line. It will be noted that this arrangement provides a traveling-pulse system which, upon firing of the switch device 38a, causes discharge of the delay line and the application of a force pulse successively to the workpiece 30. While each coil sees an electric-current pulse, it should be noted that the current wave energizes the coils in turn so that the net effect is a force wave sweeping the workpiece. This construction is only one of several delay-line arrangements which can be employed, other conventional delay-line circuits being possible with various inputand output-switching arrangements. With the aid of this type of apparatus one may reduce the cross-section of steel sheets by at a sheetdisplacement rate of about 2 m./ sec. when discharges on the order of 5000 joules/sec. are applied to the coils with a -micr0second pulse duration. The magnetic flux should be on the order of 10 gauss/ sec.

FIG. 4 shows another arrangement for energizing the coils 42a42d of a wire-drawing device. The wire 40 is drawn in the direction of arrow 49 by suitable takeup means not shown. While the coils of FIG. 3 are indicated to be in series with their respective capacitors, those of FIG. 4 form parallel-resonant networks with capacitors 46:1-4601, the network being connected in parallel across a battery 48. The capacitors are charged via a resistor 47 in series with a pulse-shaping choke 48a while a series-resonant network 48b is provided to initiate oscillations within the system. The parallel-resonant network including the coils dim-42d oscillates in phase or out of phase with the series-resonant network to apply additive pulses to the coils or current pulses derived from the phase ditference. If the characteristic frequency of the series-resonant network is much less than that of the parallel-resonant networks, a succession of axial pulses will be applied to the coils and to the workpiece. The pulses within the series-resonant network are derivedfrom alternating-current source 48c inductively coupled to the network in series with a capacitor 48d.

A somewhat modified circuit is shown in FIG. 5 wherein the coils 52a52d form parallel-resonant networks with respective capacitors 56a56d. The parallel-resonant networks are, however, connected in series with a variabletuning, series-resonant network 58b, a battery 58 and a loading resistor 57. Again an alternating-current source 58s is inductively coupled to the circuit. The parallelresonant networks can have the same or different characteristic frequencies so that the magnetic pulses form simultaneously or successively. The alternating current source 580 may be a variable-frequency oscillator connected to sensing rollers 58g, which respond to a dimension of the workpiece 50 and adjust the frequency of oscillation within the charging circuit accordingly.

In the apparatus of FIG. 7, a pair of drums 75a, 75b serve both for supply and takeup of the wire 70 and are driven by reversible motors 75c and 75d. The workpiece passes through the oppositely wound coils 71 and 72 which are serially connected across a variable-frequency alternating-current source 780. Sensing rollers 78g adjust the frequency of this source in response to dimensional changes in the wire to maintain a constant output crosssection. The wire in this case is preferably magnetically permeable so that coils 73, 74, not externally energized, can provide additional compressive action. These coils 73, 74 can form parallel-resonant networks with capacitors 76a, 76b whose characteristic frequency is half the normal frequency of source 780 so that the induced electric field within the coils 73, 74 oscillates for producing inwardly directed magnetic forming pulses. At this point it may be noted that the resultant magnetic fiux can be determined from a Fourier analysis of the individual characteristic frequencies of the several coils and their networks.

I have also found that it is possible to effectively eliminate an external source of alternating current for energizin the coils directly. To this end, an apparatus such as that shown in FIG. 8 may serve. The coil 81 may have its intermediate taps bridged by capacitors 86a, 86b, 860 although these capacitors can be dispensed with, if desired. A battery 88 applies a relatively high directcurrent magnetic field (on the order of tens of thousands of gauss) to the coil 81 which surrounds the wire 8% to be drawn. A takeup reel S5 is provided to draw the wire through the coil while a vibrator system 84 longitudinally reciprocates the wire at least at sonic frequencies but preferably supersonic frequencies, on the order of kilocycles or mega-cycles. The vibrating devices can consist of a magnetostrictive yoke 84a whose coils 84b, 84c are connected in series-aiding relationship across the AC. source 84a in parallel with a battery 8%. The magnetostrictive effect exploited in the vibrator device is that usually known as Joule magnetostriction and is distinct from the radial magnetostrictive effect which serves to reduce the cross-section of the workpiece. The device further comprises a unidirectional chuck 84 which permits the drum 85 to draw the wire therethrough. The

chuck includes an axial spring 84g having a high com pressive force which urges balls 84h against an annular wedge surface 341'. When the drum draws the wire in the direction of arrow 89, the balls 84h are frictionally urged away from the wedge surface although they engage the wire sufficiently to transmit oscillation at high frequencies in both directions.

Example III An electric transmission wire having a steel core of 6 mm. in diameter and an aluminum sheath, whose radial thickness is 1 mm., is reduced to a total diameter of 7.5 mm. by five passes through a single SOO-turn coil 81 (the capacitors 86a-86c being dispensed with) or a single pass through five coils each having 500 turns. The directcurrent magnetic field at each coil is 20,000 gauss and the wire is vibrated at a frequency of 55 kc./sec. with a longitudinally vibrational stroke of 25 microns. The drawing speed is 2 m./sec. The resulting transmission line is found to have better physical properties than wires produced with equal quantities of aluminum and steel at high temperatures and has from to greater tensile strength without reduction of conductivity.

To provide servo control of the output diameter of the wire, the detectors 88g effect adjustment of the drawing speed by regulating a variable-speed motor 85a, in a conventional manner, this motor driving the takeup drum 85.

In FIG. 9 the forming coil 91 is center tapped and connected in series with a variable-frequency source 980 and a pair of capacitors 96a, 9617. Both halves of the coil thus apply pulses during each cycle of the source 980, although in opposite senses. This reversal of senses merely alters the effective axial direction of the magnetic field and does not diminish the radial or pinch force. The arrangement shown in FIG. 9, as in the apparatus of FIG. 8, prevents a net axial displacement of the wire as consequence of the flux of the coils 71, 72 and 91. The frequency of source 98c is again controlled by a servo in accordance with the output dimension of the wire via a sensor 98g.

In the device of FIG. 10, only part of the coil 101 is bridged by the alternating-current source 1080 while the full coil is connected in parallel with a phase-shifting capacitor 106. This capacitor causes a parametric oscillation within the entire coil as a consequence of excitation of a part thereof by the source 108C. The pulse applied to the workpiece 100 is thus the resultant of the oscillations of source 1080 and the parametric oscillation 101, 106.

FIG. 11 illustrates a modified method of bonding an outer sheath 11017 to a core 110a of the workpiece 110. I have discovered that it is possible to carry out this bonding action without the aid of a radially directed magnetic field although such a field proves an asset in this arrangement. The bonding is effected by relatively oscillating the portions 1100, 110b at sonic or supersonic frequencies to cause the development of sufficient frictional heat at the interface that fusion welding takes place. Although an electromechanic transducer can be used for supplying the necessary vibrations (e.g. the vibrating device shown in FIG. 8), I prefer to employ the axial oscillations derived from the magnetic field of a coil 111. This coil is connected in series with a spark gap 118w and a directcurrent source 118 via a charge resistor 117 and a capacitor 116. A tuning capacitor 116a bridges part of the coil to establish a resonant circuit therewith. With breakdown of the spark gap, a high-frequency alternating current is applied to the coil 111 which establishes a mechanical wave of oscillation within the core 110a. This mechanical oscillation is essentially a rare-faction and condensation wave which, for purposes of convenience, is illustrated as a sine wave 1100. As the core 110a shifts slightly within sheath 110b, high frictional-heat evolution results at the interface to cause bonding of the outer layer to the core. Best results are obtained when the vibration wave travels the length of the wire and is not simply a standing wave.

8 Example IV Using a device such as that shown in FIG. 11, a sheath of aluminum having a 1 mm. thickness was bonded to a steel core having a diameter of 6 mm. by applying to the core a frequency of kc./sec. and 1 mc./sec. After a treatment time on the order of several seconds, the aluminum layer in the region of the source of oscillation was found to be firmly bonded to the steel core although some fissures did occur with repeated bending tests. Such fissures were eliminated when an additional magnetic pinch forming was used.

The invention described and illustrated is believed to admit of many modifications within the ability of persons conversant with the art, all such modifications and variations being considered within the spirit and scope of the appended claims.

I claim:

1. A method of shaping metallic bodies, comprising the steps of heating an elongated magnetically permeable metallic body to bring it to a plastically deformable state along at least a portion of said body; surrounding said portion with a plurality of longitudinally arrayed electromagnetic coils; reducing the cross-section of said body along said portion by successively supplying electric current pulses to said coils, thereby applying to said body inwardly directed magnetic force sweeping said portion; substantially continuously drawing said body through said coils during application of said magnetic force; and longitudinally oscillating said body during the passage of electric current through said coils to induce said electric current in at least one of said coils by the oscillations of said body.

2. A method as defined in claim 1 wherein said pulsed electric current is derived from the resultant of at least two alternating-current signals in out-of-phase relationship applied across said coil.

3. A method as defined in claim 1 wherein each of said coils forms part of a resonant network and said pulsed electric current is derived from current oscillation in said network.

4. A method as defined in claim 1, further comprising the step of controlling at least one parameter of said electric current in response to a dimension of said body passing out of at least one of said coils.

5. A method as defined in claim 1 wherein said body is heated to a plastically deformable state by inductive elfeot of at least one of said coils.

6. An apparatus for shaping a magnetically permeable metallic body, comprising a plurality of axially spaced aligned coils, means for drawing said body through said coils substantially continuously; circuit means including respective capacitive means associated with and individual to each of said coils and forming therewith respective resonant networks; and a source of shaping pulses connected with said circuit means for pulsatingly energizing same for generating current surges consecutively through the successive coils spaced along said body and the resonant networks individual to said coils.

7. An apparatus as defined in claim 6, further comprising means independent of said coils for heating said body to a plastic state.

8. An apparatus as defined in claim 6, further comprising means for continuously drawing said body through said coils While said coils apply successive induction pulses to said body.

9. An apparatus as defined in claim 6, further comprising means for vibrating said body in generally axial direction at least at sonic frequencies.

10. An apparatus as defined in claim 9, further comprising another coil surrounding said body and capacitive means forming a resonant network with said other coil energizable upon vibration of said body.

11. An apparatus as defined in claim 6, funther comprising means responsive to a dimension of said body after the forming thereof for controlling at least one parameter of the electrical energy supplied to at least one of said coils.

12. An apparatus for shaping a metallic body, comprising a plurality of axially spaced aligned coils, means for drawing said body through said coils substantially continuously; and circuit means for successively energizing said coils with high-energy electrical pulses to magnetically shape said body, said circuit means including respective capacitive means associated with each of said coils and forming therewith a resonant network, said circuit means forming a delay line with said coils.

References Cited by the Examiner UNITED STATES PATENTS Harvey 153-10 Tramm et a1. 7892.1

Birdsall et al. 29-421 Harvey 153-10 Harvey et al. 18-165 Brower et a1. 29421 10 CHARLES W. LANHAM. Primary Examiner. 

6. AN APPARATUS FOR SHAPING A MAGNETICALLY PERMEABLE METALLIC BODY, COMPRISING A PLURALITY OF AXIALLY SPACED ALIGNED COILS, MEANS FOR DRAWING SID BODY THROUGH SAID COILS SUBSTANTIALLY CONTINUOUSLY; CIRCUIT MEANS INCLUDING RESPECTIVE CAPACITIVE MEANT ASSOCIATED WITH AND INDIVIDUAL TO EACH OF SAID COILS AND FORMING THEREWITH RESPECTIVE RESONANT NETWORKS; AND A SOURCE OF SHAPING PULSES CONNECTED WITH SAID CIRCUIT MEANS FOR PULSATINGLY ENERGIZING SAME FOR GENERATING CURRENT SURGES CONSECUTIVELY THROUGH THE SUCCESSIVE COILS SPACED ALONG SAID BODY AND THE RESONANT NETWORKS INDIVIDUAL TO SAID COILS. 